Underreamer



R. C. BAKER UNDERREAMER April 17, 1951 Filed April 4, 1947 Patented Apr. 17, {951 UNITED STATES PATENT. OFFICE UNDERREAMER Reuben C. Baker, Coalinga, Calif., assignor to Baker Oil Tools, Inc., Vernon, Calif., a corporation of California Application April 4, 1947, Serial N 0. 739,403

14 Claims.

sion. This is particularly'true of cutters of the.

drag type, which are held confined within slots in the underreamer body, and in which the rotary drilling mud tends to pack firmly between thecutters and the sides of the slot, in effect freezing the cutters to the body.

Accordingly, it is an object of the present invention to provide an underreamerwhose cutting elements can be expanded outwardly with greater facility, and in which the tendency of the cutting elements to become wedged or frozen to the underreamer body is largely, if not entirely, eliminated.

Another object of the invention is to'provide an underreamer whose cutter blades are expanded outwardly, and in which the expansion of the bladesthemselves removes or eliminates any substances, such as drilling 'mud, which may havebecome wedged between and-the underreamer body. i

One form which theinvention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which:

Fig. 1 is a longitudinal section through an underreamer, with its cutter blades shown in elevation and in retracted position.

Fig. 2 is a partial side elevation of the underreamer disclosed in Fig. 1.

Fig. 3 is a cross-section taken along the line 3- -3 in Fig. 2, with the cutter blades in retracted.

position.

Fig. 4 is a view similar to Fig. 3, disclosing the cutter blades in expanded position.

Underreamers of the type disclosed in the drawings are described in detail in United States Patent No. 1,857,616. They include an elongate main supporting body lllprovidedwith an upper threaded box H attachable to the lower end of a, string of drill pipe l2 or the like, by means-of whichthe underreamer is lowered in the well bore and rotated in the performance the blades mounted between the legs.

each link is pivotallyattached to a cutter blade 1 l5 by means of a pin 24. It is to be noted that" the links 23 are pivoted tothef blades on op-u posite sides of the hinge pin IS in orderthat-" downward movement of the plunger [9 pivots the blades 15 oppositely'in upward and out- 5 ward directions. Such outward movementmay of its underreaming operations. The body has a central longitudinal passage l3 therethrough merging into a lower elongate slot llopeningoutwardly of the body. A pair of cutter blades 15 of the drag type are movable within the slot 14 being mounted upon a hinge pin I6 extend-"- ing through the body and across its slot [4.

The cutters I5 have an initial downward po-, sition substantially completely retracted within the confines of the body land are swingable outwardly inlopposite directions to extend beyond the periphery of the body, occupying a generally horizontal position with their upper sides l5a engaging the upper shoulders, I! of the longitudinal slot- M. A second set of'longitudinal slots lflextend upwardly to one side of and above the stop shoulders I! at the ends of the main slot M to provide passages throughwhich drilling fluid may pass for discharge onto the cutter blades IS.

The blades are swingable inwardly and outwardly of the body slots M in response to up-f.

ward and downward movement of .an operatingplunger l9 slidable within the central'pas;

sage 13' of the main body. This plunger in cludes a tubular plunger body 20 having, a trans.-

verse hole through depending legs 2| in its lower. end for receiving'a pivot pin-22 in which the.

upper Gl'ldSxOf a pair of'links 23 are pivotally The lower end of continue, as aforementioned until the blades occupy horizontal positions in contact with the body shoulders I1.

The upper end of the body passage I3 is en larged in diameter to form a cylinder 25 slidably receiving the upper piston portion 26 of the plunger, which is also enlarged to a diameter; greater than the lower body portion '20.. -A -plu-i. rality of piston rings 21, of, rubber or similar. material, are mounted on the-piston for slidable"; sealing engagement with the .wall ofthe cyl inder 25'to prevent leakage in both directions" around the piston. A spring 28 encircles the smaller diameter plunger body portion 2ll,"one end engaging the lower end 29 of the cylinder, and its other end engaging the piston 26; This spring is under compression and 7 tends to elevate the plunger I9 and retract and 3 maintain the blades I5 in their inward position within the confines of the body I against longitudinally extending stops I40 welded to the sides of the slot I4 adjacent its outer ends.

The plunger I9 is movable downwardly and the blades expanded outwardly by the pressure of fluid, like drilling mud, pumped downwardly through the string of drill pipe I2 and acting upon the piston 26. Since it is desired to discharge the drilling fluid onto the cutters 15 to maintain them free of detritus, the fiuid continues downwardly through a central passage 30 in the plunger I9 for discharge in opposite directions through elongate slots 3i in the lower portion of the plunger body and through the upper body slots I8 onto the forward cutting faces Ib of the cutter blades I5. In viewof this .jdiscross-section away from the back face I5c of the blade inthe direction in which the blades are expanded outwardly. In effect, such relief is V-shaped or wedge shaped in cross-section. The relief, however, does not extend along the upper portion I ib of the slot sides, which are parallel to the trailing faces I50 of the blades I5 and adapted to engage such bladesfaloiag a substantial area of contact.

The underreamer is run in the well bore with the blades I5 in retracted positions and with their charge of fluid, an orifice or restriction 33 is provided in the plunger passage 30 to enable a back pressure to be built up on the high pressure side of the piston 26 sufiicient in value to overcome the compressive force of the spring 28, shift the plunger I9 downwardly, and swing the blades I5 outwardly through the agency of the pin and link connections 22, 23, 25 between the plunger I9 and blades I5. A slotted screen 4! may also be provided above the orifice 33 to prevent plugging of the latter.

Heretofore the sides'of the slot I4 have been made parallel to one another and to the sides of the fiat cutter blades throughout their length, and have had substantial sliding engagement with the blades upon outward expansion of the latter" in order thatthe backor trailing faces 150 of the blades would be engaged directly by the main body of the underreamer during rotation of the tool in the performance of the underreaming operation. Such support would prevent bending or breaking of the blades under high torque operating conditions. Despite the desirability for having such firm backing on the blades by the body, the trailing faces I5c of the blades were in comparatively snug engagement with the sides of the slot I4. Under some hole conditions, drilling mud would pack between the blades I5 and'the sidesof'the slot I4 while the blades. were in retracted position, and during their lowering through the'drillin'g mud in the well-bore to the locationat which underreaming was to be performed. The extent of suchpacking :or wedgingofthe drilling fund is oftentimes such as-to prevent outward expansion of the blades I5 from'their retracted'positions upon the subjection of high pressures to the piston 26 of the plunger I9, the blades remaining in their retra'cted positions andun'available for the performance of the underreaming .functbn. As a result, removal of the underreamer from the well bore was required for the'purposeof freeing the blades, at a substantial economic loss, and without assurance that they would be expandible upon rerunningin the well.

By virtue of the present invention, it is pr'oposed to effect relief between the blades I5 and the'sides of the slot I4, to eliminatethe wedging tendency of the drilling mud onthe blades" and to enable. their expansion whenever sufiicient hydraulic pressur is imposed on the plunger piston However, the blades I5 would still have sunlcient backing upon their outward expansion to the horizontal position.

As disclosed in the drawings, the lower portion of the side of the slot I4 adjacent the back face lie of each blade is relieved to provide an elongatelaterally taperedsurfac'e Ma inclined in lower sides I5d disposed longitudinally and in engagement with the longitudinal ribs or stops I4c. During 'therun'ning of the tool in the well bore to the desired-- location, drilling mud and other substances may pack around the blades I5 within the body slot I4 and may completely fill the wedge shaped relief portions of the slot betweenthe trailing faces I50 and the inclined surfaces Ma, being packed firmly between such faces and tapered relieving surfaces. Upon reaching the location in the well bore at which the underreaming operation is to commence, the pumps are started at the surface of the well bore and fluid pressure imposed on the piston 26, forcing it downwardly against the action of the :retractor spring 28 and tending to swing the cutter blades I5 in opposite directions upwardly and outwardly of the body slot I4. It is to be. noted that the initial portion of the outward. swinging of the blades will move the packed mud.

out of the wedge shaped relief portion ofthe body slot I L-since the slightest movement willmove the V-shaped mud pack toward a larger space between the back face I5c of each blade and the tapered side I la of the relieved area. Following this initial movement, the blades I5 may be swung outwardly to their fullest extent and horizontal position, without interference. from with their trailing faces I50 in snug engagement with the unrelieved upper sides Mb of the "slot I4, such sides 14b providing a firmbacking to the blades-during their rotation and operation upon the formation material in the well bore.

It is,accordingly, apparent that an under-1 reamer has been provided in which, wedging of the blades by the drilling mudand othersub-w stances in the well bore-is largely, if notentirely; eliminated, thereby insuring" theexpansion of the' blades to the fullest extent when and where desired. Despite the relief. of the sides of the slot M to accomplish the aforementioned purpose, the blades have full backiiigby the body for'the purpose of transmitting the. drilling torque directly from theb'ody to'the blades themselves.

While I have shown'the preferredfcrm-bfmy invention, it is to be understood '*thatvaridiis changes may be 'made "miss-ccnstruetion by the spirit of the invention as defined in the s;

those skilled i'n'th'e art'wimtut departingpended claims. A

Having thus'desciibed my invention, what 'I' claim and desire to secure by Letters Patent is:

"1.' An underreanier, including a'p qy gaa g for attachment to a drill "string, said tony having a transverse slot, initially'retracted cutter meanl t' within said s1ot,rheaiis connected to said cutter means for moving said outt'er meansdn a single; central plane within said slot laterally utwarc I of said body; said cutter means having a ifiar ginal portion providing a'cutting edge and an opposite marginal portion facing outwardly of said body, in the direction in which said cutter means is moved, when said cutter means is disposed in retracted position within said slot, said cutter means and side of saidslot having a relieved portion whose surface is inclined in crosssection to the plane of movement of said cutter means within said slot for facilitating such lateral outward movement of said cuttermeans.

2. An underreamer, including a body adapted for attachment to a drill string, said body. having a transverse slot, an initially retracted flat cutter blade mounted within said slot, means connected to said cutter blade for moving said blade in a single central plane within said slot laterally outward of said body, said cutter blade having a marginal portion providing a cutting.

edge and an opposite marginal portion facing outwardly of said body, in the direction in which said blade is moved, when said blade is disposed in retracted position within said slot said cutter blade and side of said slot having a relieved portion whose surface is inclined in cross-section to the plane of movement of said cutter blade with-.- in said slot for facilitating such lateral outward movement of said blade.

3. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, an initially retracted fiat cutter blade pivotally carried by said body within said slot, means connected to said cutter blade for swinging said blade in a single central plane within said slot laterally outward of said body, the side of said slot adjacent said cutter blade having a relieved portion whose surface is inclined in cross-section to the adjacent side of said cutter blade for facilitating lateral movement of said blade outwardly of said body.

4.-An underreamer, including a'body adapted for attachment to a drill string, said body having a transverse slot, a cutter blade pivotally carried by said body within said slot, means connected to said blade for swinging it outwardly of said body to expanded position, the lower portion of the side of said slot adjacent the trailing face of said blade being relieved to facilitate outward swinging of said blade, the upper portion of the side of said slot being unrelieved to contact said trailing face and transmit rotary motion of said body directly to said blade following .outwar expansion of said blade.

5. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a cutter blade pivotally carried by said body within said slot, means con nected to said blade for swinging it outwardly of said body to expanded position, the side of said slot adjacent the trailing face of said blade having a lower relieved portion whose surface is inclined in cross-section to the adjacent trailing face of said cutter blade, said inclined surface diverging from said trailing face in the direction of outward swinging of said blade, the upper portion of the side of said slot being unrelieved and parallel to said trailing face to contact said trailing face and transmit rotary motion of said body directly to said blade following outward expansion of said blade.

6. An underreamer, including a body adapted for attachment to a drill string, said body havbody to expanded positions, the lower portions of the sides of said slot adjacent the trailing faces ofjsaid blades being relieved to facilitate outward swinging of said blades, the upper portions of the sides of said slot being unrelieved to contact said trailing faces and transmit rotary mo-.

tion of said body directly to said blades following their outward expansion.

7 An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a pair of cutter blades pivotally carried by said body within said slot, means connected to said blades for, swinging them in opposite directions outwardly of said body to expanded positions, the lower portions of the sides of said slot adjacent the trailing faces of said blades being each inclined in cross-section to the adjacent trailing face of a cutter blade, said inclined'portion diverging from said trailin face in the direction of outward swinging of said blade, the upper ,portions of the sides of said slot being unrelieved and parallel to said trailing faces to contact said trailing faces and transmit rotary motion of said body directly to said blades following their outward expansion.

8. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot whose upper portion constitutes a shoulder, a pair of cutter blades pivotally carried by said body and adapted for disposition vertically within said slot, means connected to said blades for swinging them in opposite directions outwardly of said body to horizontal positions in engagement with said shoulder, the lower portion of the sides ofsaid slot adjacent the trailing faces of said blades being each inclined in cross-section to the adjacent trailing face of a cutter blade, said inclined portion diverging from said trailing face in the direction of outward swinging of said blade, the.

upper portions of the sides of said slot being unrelieved and parallel to said trailing faces to contact said trailing faces and transmit rotary motion of said body directly to said blades following their outward expansion into engagea transverse slot, an initially retracted fiat cutter blade pivotally carried by said body within said slot, means connected to said cutter blade for swinging said blade in a single central planet within said slot laterally outward of said body; said cutter blade having a marginal portion providing a cutting edge and an opposite mar-.;

ginal portion facing outwardly of said body, in the direction in which said body is swung, when said blade is disposed in retracted position within said slot, the side of said slot adjacent said blade having a relieved portion whose surface is inclined in cross-section to the adjacent side of said cutter blade for facilitating lateral movement of said blade outwardly of said body.

10. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a cutter blade pivotally carried by said body within said slot, means connected to said blade for swinging it outwardly of said body to expanded position, said cutter blade having a marginal portion providing a cutting edge and an opposite marginal portion facing outwardly of said body, in the direction in which said blade is swung, prior to swinging of said blade outwardly of said body, the lower portion of the side of said slot adjacent the trailing face merges? of said bladebein'g relievedto facilitate outward swinging of said blade, the upper portion of the side of said slot being unrelieved to contact said trailing face and transmit rotary motion of said body directly to said blade following outward ex-- pension of said blade.

11. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a cutter blade pivotally carried by said body within said slot, means connected to said blade for swinging it outwardly of said body to expanded position, said cutter blade having a marginal portion providing a cutting edge and an opposite marginal portion facing outwardly of said body, in the direction in which said blade is swung, prior to swinging of said blade outwardly of said body, the side of said slot adjacent thetr'ailing face of said blade having a lower relieved portion whose surface is inclined in cross-section to the adjacent trailing face of said cutter blade, said inclined surface diverging from said trailing face in the direction of outward swinging of said blade, the upperportion of the side of said slot being unrelieved and parallel to said trailing face to contact said trailing face and transmit rotary motion of said body directly to said blade following outward expansion of said blade.

12. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a pair of cutter blades pivotally carried by said body within said slot,means connected to said blades for swinging them in opposite directions outwardly of said body to expanded positions, each cutter blade having 'a marginal portion providing a cutting edge and an opposite marginal portion facing outwardly of said body, in the direction in which said blade is swung, priorto swinging of said blade outwardly of said-body, the lower portions of the sides of said slot adjacent the trailing faces of said blades being relieved to facilitate outward swinging of said blades, the upper portions of the sides of said slot being unrelieved to contact said trailing faces and transmit rotary motion of said body directly to said blades following their outward expansion.

13. An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot, a pair of cutter blades pivotally carried by said body within said slot, means connected to said blades for swinging them in opposite'directions outwardly of said body to expanded positions, each cutterblade having a marginalportion providing a cutting edge and an opposite marginal portion facing outwardly ofsaid body, in the direction in which said blade is swung, prior to swinging of said blade cut wardly of said body, the lower portions of the sides of said slot adjacent the trailing faces of said blades being each inclined in cross-section to the adjacent trailing face of a cutter blade, said inclined portion diverging'from said trailing face in the direction of outward swinging of a said blade, the upper portions of the sides of said slot being unrelieved and parallel to said trailing faces to contact said trailing faces and transmit rotary motion of said body directly to said blades following their outward expansion.

14; An underreamer, including a body adapted for attachment to a drill string, said body having a transverse slot whose upper portion constitutes a shoulder, a pair of cutter blades pivotally carried by said body and adapted for disposition vertically within said slot, means connected to said blades for swinging them in opposite directions outwardly of said body to horizontal positions in engagement with said shoulder, each cutter blade having a marginal portion providing a cutting edge and an opposite marginal portion facing outwardly of said body, in the direction in which said blade is swung, when said blade is disposed vertically within said slot, said opposite marginal portion engaging said shoul REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,669,467 Harris May 15, 1928 1,764,373 Wells June 17, 1930 1,857,616 Baker May 10, 1932 1,858,263 Charlton May 17, 1932 1,955,631

Harris Apr. 17, 1934 

